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Unhexpentium
'''Unhexpentium, '''Uhp, is the temporary name for element 165. NUCLEAR At least one set of theoretical values for half-lives and decay modes of Uhp have been constructed for neutron count up to N = 333(1). It predicts isotopes in a band ranging from Uhp 450 to Uhp 484. Examination of pp 15 & 18 of Ref. 1 indicates that Uhp 450 through Uhp 453 have sub-microsecond half-lives and decay by fission. Uhp 454 to Uhp 463 have sub-millisecond half-lives and decay mainly by alpha emission. Uhp 464 to Uhp 474 apparently decay by alpha emission and have half-lives ranging up to around 1 sec. Isotopes between Uhp 475 to Uhp 484 also decay by alpha emission, but have short half-lives. Beyond Uhp 484 the model appears to indicate a band of short-lived, fission-decaying drops, only a few of which can be considered isotopes of Uhp. These predictions are to be expected for neutron shell closure at N = 308. What Ref. 1 can’t do is describe heavy isotopes of Uhp. It is possible to use a first-order, liquid-drop approach to guess at the amount of structural correction energy needed to allow a drop of nuclear matter to survive for the 10^-14 sec needed for electromagnetic interactions (such as binding an electron) to become important. At least two computations of the neutron dripline’s location up to Z = 175 exist(2),(3), and since they give similar results, the maximum possible size of a Uhp nucleus can be set slightly above the values computed, allowing only a small margin for error. This gives Uhp 589 as the heaviest possible Uhp isotope. Structural correction required for Uhp 589 itself is around 0.5 MeV, which means all Uhp drops will fission quickly without structural stabilization. In general, it is not possible to describe structural correction energy. What can be predicted are neutron and proton shell closures, for which correction energy is expected to be particularly large. Neutron shell closures have been predicted at N = 406(3),(4), 370(3), 318(5), and 308(1). The isotope Uhp 571 requires around 1.25 MeV of structural correction, which means isotopes in the Uhp 561 to Uhp 576 band are likely. (See “Formation” for additional significance of these nuclei.) Uhp 536 requires around 1.5 MeV of structural correction, which means isotopes in the band Uhp 525 to Uhp 540 are also likely. All isotopes in both bands should beta-decay with half-lives under a second. On the other hand, Uhp 483 requires around 2 MeV of correction energy, which means alpha-decaying nuclei are likely in the band Uhp 473 to Uhp 488. Ref. 1 does not show a pattern of nuclides which indicate a shell closure at N = 318. ATOMIC Several predictions for the ground state electron structure of Uhp agree that it will have alkali metal character, with a 9s electron the main one available for bonding. It's 7d electrons might also participate. Electrons in Uhp can be described in terms of time-independent orbitals, but calculation of electron properties require that nuclear charge be distributed over the nucleus' actual volume. In addition, there is some chance that differing nuclear shapes may produce different electron configurations in different isotopes. (Different isotopes would be different elements in the chemical sense.) Except in the laboratory, Uhp is expected to exist only in environments too hot for ordinary chemistry to occur. FORMATION Ions of this element may form when material from roughly 1 km depth is ejected from a disintegrating neutron star during a merger. There is a possibility that beta decay from dripline nuclides stabilized by the N = 406 closure, enhanced by the Z = 164 proton shell closure, will allow some isotopes in the vicinity of Uhp 560 to Uhp 577 to form in quantity during such a merger. It improbable that nuclides between Uhp 525 and Uhp 540, or lighter, can form in this way. Fusion or multinucleon transfer reactions in the polar jets emanating from a neutron star or black hole might produce lighter isotopes, including those in the Uhp 450 to Uhp 484 band. Quantities produced by this method are very small. REFERENCES 1. "Decay Modes and a Limit of Existence of Nuclei"; H. Koura; 4th Int. Conf. on the Chemistry and Physics of Transactinide Elements; Sept. 2011. 2. "Neutron and Proton Drip Lines Using the Modified Bethe-Weizsacker Mass Formula; D.N. Basu et al; Int.J.Mod.Phys.; arXiv:nucl-th/0306061; url: https://arxiv.org/abs/nucl-th/0306061 3. “Single Particle Levels of Spherical Nuclei in the Superheavy and Extremely Superheavy Mass Region”; H. Koura and S. Chiba; Journal of the Physical Society of Japan; DOI 10.7566/JPSJ.82.014201; Jan. 2013. 4. "Magic Numbers of Ultraheavy Nuclei"; V. Yu Denisov; Physics of Atomic Nuclei, v. 68, no. 7, pp 1133-1137; 2005. 5. “The Highest Limiting Z in the Extended Periodic Table”; Y.K. Gambhir, A. Bhagwat, and M. Gupta; Journal of Physics G: Nuclear and Particle Physics. 42 (12): 125105. DOI:10.1088/0954 3899/42/12/ 125105. (12-13-19) Category:Undiscovered elements Category:Period 9 Category:Alkali metals Category:Radioactive